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    <script>
        console.log(2 > 3);     //false
        console.log(3 >= 3);        //true
        console.log(2 == 2);        //true
        //比较运算符右隐式转换，把"2"转换为2，上等号只判断值
        console.log(2 == "2");      //true
        console.log(undefined == null);       //true
        console.log(undefined === null);      //false
        // ===全等判断值和数据类型都一样才行
        // 以后判断是否相等，请用===
        console.log(2 === "2");       //false
        console.log(NaN === NaN);       //false NAN不等于任何人
    </script>
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